1. Field of the Invention
The present invention relates to an electromagnetic actuator intended for moving an object.
2. Description of the Prior Art
Actuators for moving an object, typically conveyor and the like, are known from the disclosures in the Japanese Patent Application Laid Open Publication Nos. 258013/1985 and 166429/1986.
The actuator of such type has a moving path body made of a material selected among Fe, Cu, Al, etc. under which there is provided a plurality of ultrasound transducers each comprising a piezoelectric element. When a voltage is applied as phase-shifted to these ultrasound transducers, a surface traveling wave is produced in the moving path body to move an object placed thereon.
However, these conventional actuators are disadvantageous in that since they use the piezoelectric elements as electromechanical transducers, the drive voltage must be raised to several thousands volts for application as a high frequency voltage to the piezoelectric elements in order to minimize the displacement and increase the moving speed. Also because the piezoelectric element has a small amplitude of vibration, the moving path body surface of contact with the ultrasound transducers and that with an object to be moved must be shaped with a high precision and machined to a precise surface roughness, and a displacement increasing mechanism is necessary in addition. Further, such actuator generates an audible sound, and because the piezoelectric element used in the actuator is relatively fragile, the actuator cannot easily be assembled or mounted in an equipment.
Also the Japanese Patent Application Laid Open Publication No. 299785/1988 discloses an actuator of translation type. The actuator known from this Publication comprises a moving member, a piezoelectric element fixed to the end of the moving member and an inertia body which is driven by the piezoelectric element to give a shock to the moving member. The expansion or shrinkage of the piezoelectric element impulsively moves the inertia body of which the reaction is utilized to cause the moving member to make an inching motion. However, this actuator also has similar disadvantages to those of the above-mentioned conventional techniques, and so it can only be used as a micro-movement means in positioning and the like.